Quiet snowmobile

ABSTRACT

Disclosed herein is a snowmobile including a hood extending from a frame portion to a transverse partition extending upwardly from the frame portion and defining, with the frame portion and with the transverse partition, a substantially closed compartment, together with first wall means extending in the compartment and dividing the compartment into an air supply chamber and an exiting air chamber, second wall means extending in the air supply chamber and dividing the air supply chamber into an entering air sub-chamber and a carburetor air supply sub-chamber communicating with the entering air sub-chamber, and an internal combustion engine mounted on the frame within the compartment and including a pair of cylinders, an engine cooling system including means defining an engine cooling air passage communicating between the entering air sub-chamber and the exiting air chamber, and a carburetor operably communicating with the cylinders and including an air inlet communicating with the carburetor air supply sub-chamber. The snowmobile disclosed herein also includes separate first and second mufflers mounted on the frame in the exiting air chamber and connected to the respective exhaust ports of the cylinder, together with baffled air inlet means communicating with the air supply chamber and baffled air outlet means communicating with the exiting air chamber. The mufflers disclosed herein each include a series of barriers dividing the muffler into a series of chambers with one of the chambers including a single exhaust megaphone and with another of the chambers including a perforated barrier adjacent to one of the end walls of the muffler.

United States Patent 1191 Smale Dec. 10, 1974 QUIET SNOWMOBILE [75]Inventor: William B. Smale, Cedarbury, Wis.

[73] Assignee: Outboard Marine Corporation,

Waukegan, Ill.

[22] Filed: Mar. 14, 1974 [21] Appl. No.: 451,203

Related US. Application Data [62] Division of Ser. No. 258,260, May 51,1972, Pat. No.

52 us. (:1. .Q 181/53,'181/57 3,687,225 8/1972 Nelson 181/53'x 3,703,93811/1972 Nelson 181/53 x 3,786,897

1/1974 Swanson 181/54 Primary Examiner Richard B. Wilkinson AssistantExaminer-John F. Gonzales Attorney, Agent, or Firm-Michael, Best &Friedrich [57] 1 ABSTRACT Disclosed herein is a snowmobile including ahood extending from a frame portion to a transverse partition extendingupwardly from the frame portion and defin l i t ing, with the frameportion and with the transverse partition, a substantially closedcompartment, together with first wall means extending in the compartmentand dividing the compartment into an air supply chamber and an exitingair chamber, second wall means extending in the air supply chamber anddividing the air supply chamber into an entering air subchamber and acarburetor air supply sub-chamber communicating with the entering airsub-chamber, and an internal combustion engine mounted on the framewithin the compartment and including a pair of cylinders, an enginecooling system including means defining an engine cooling air passagecommunicating between the entering air sub-chamber and the exiting airchamber, and a carburetor operably communicating with the cylinders andincluding an air inlet communicating with 1 the carburetor air supplysubchamber. The snowmobile disclosed herein also includes separate firstand second mufflers mounted on the frame in the exiting air chamber andconnected to the respective exhaust ports of the cylinder, together withbaffled air inlet means communicating with the air supply chamberandbaffled air outlet means communicating with the exiting air chamber.

The'mufflers disclosed herein each include a series of barriers dividingthe muffler into a series of chambers with one of the chambers includinga single exhaust megaphone and with 1 another of the chambers includinga perforated barrier adjacent to one of the end walls of the mufiler.

3 Claims, 6 Drawing Figures QUIET SNOWMOBILE This is a division ofapplication Ser. No. 258,260 filed May 31, 1972, now Pat. No. 3,810,518,

, BACKGROUND OF THE INVENTION The invention relates generally tosnowmobiles and particularly to arrangements for reducing noiseemanation from snowmobiles. The invention also relates to mufflers.

Although snowmobiles have enjoyed increasing popularity in the recentyears, nevertheless snowmobiles have been subject to increasingcriticism as being excessively noisy. The invention is directed towardeliminating or reducing this criticism. Reduced snowmobile soundemanation is achieved with the invention by modification of conventionalsnowmobile construction and by improvement in muffler construction.

SUMMARY OF THE INVENTION The invention provides a snowmobile in whichthe engine compartment, under the hood forwardly of the dashboard, isconstructed so as to be, except for one or more baffled-inlets andoutlets, substantially closedand airtight so as to retain therein,noises generated by engine operation and in which the substantiallyclosed engine compartment is divided by suitable wall means into an airsupply chamber communicating with a baffled inlet and an exiting airchamber which communicates with a baffled air outlet and with the airsupply chamber through the cooling system of an internal combustionengine located in the engine compartment.

' sub-chamber and with the carburetor air inlet.

Various snowmobileshave coventionally employed two cylinder engines and,in accordance with the invention, separate mufflers are provided foreach cylinder and are located in the exiting air chamber of the enginecompartment and in physically parallel relation to each other. Inaddition, in accordance with the invention, mufflers of improvedconstruction are provided. More specifically, in this last regard, amuffler in accordance with the invention includes a single megaphonechamber with a single megaphone having an outlet adjacent to an end wallof the muffler. In addition to the megaphone chamber, a muffler inaccordance with the in vention is sub-divided, in axially adjacentseries, into a central chamber, an outlet chamber and an end chamber.Pipe means are arranged so that exhaust gas flow is from the megaphonechamber to the central chamber, then to the end chamber where thedirection of flow is reversed, then to the outlet chamber, and then intothe exhaust outlet pipe. In addition, in accordance with the invention,the end chamber includes in adjacently spaced relation to the end wall.a baffle which is perforated so that it is approximately 50 percentopen.

Also in accordance with the invention, the battery and the fuel pump ofthe snowmobile are preferably located in the air supply chamber ascompared to the exiting air chamber so as to avoid the highertemperatures found inthe exiting air chamber.

Also in accordance with the invention, the carburetor air supply chamberis formed so as to have a volume which is at least as great as the totalpiston displacement of the associated engine.

Also in accordance with the invention, the air supply camber and theexiting air chamber include various means for causing change in thedirection of flow of air so as to assist in reducing transmission ofnoise. These means include formation of the chambers and subchambersthemselves, the use of baffles, such as the air inlet and exiting airbaffles, as well as baffles in the subchambers, the use of othercomponents as baffles, i.e., for instance, the battery, and the use ofscreened ports and rotary deflectors.

Another of the aspects of the invention resides in the employment of themufflers in the exiting air chamber and the provision for circulation ofair within the exiting air chamber so as to help reduce the temperatureof the mufflers and thereby extract a greater amount of heat from theexhaust and thereby reduce the exhaust noise.

A still further object of the invention is the arrangement by which theexhaust outlet pipes from the mufflers pass through the bottom wall ofthe engine compartment for discharge of exhaust gases underneath thesnowmobile.

Still another feature of the invention is the use of sound absorbinglining interiorly of the engine compartment and in connection with thebaffled inlet and outlet ports.

One of the objects of the invention is the provision of an improvedsnowmobile constructed so as to operate at a substantially reduced noiselevel.

Another of the principal objects of the invention is the provision of anew and improved muffler having significant noise reduction capabilitieswithout causing adverse reduction in engine horsepower output.

Another of the principal objects of the invention is the provision of anarrangement for circulating air inside ot the engine compartment of asnowmobile.

Another of the principal objects of the invention is the provision of anarrangement for preventing vapor lock and overheating of the fuel pumpand battery of a snowmobile.

Another of the principal objects of the invention is the provision of anarrangement for supplying air to a carburetor so as to substantiallyreduce or eliminate emanation from the snowmobile of carburetor intakenoise.

Other objects and advantages of the invention will become known byreference to the following descrip tion and accompanying drawings.

, I DRAWINGS FIG. 1 is a fragmentary perspective view partially brokenaway and in section of a snowmobile embodying various of the features ofthe invention.

FIG. 2 is a fragmentary view partially broken away and in section of aportion of the apparatus shown in FIG. 1.

FIG. 3 is an enlarged axial sectional view of one of the mufflersincluded in the construction shown in FIG. I.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 3.

FIG. 6 is a fragmentary. sectional view taken along line 6-6 of FIG. 1.

Before explaining the invention in detail, it is to be understoodthatthe invention is not limited in its application to the details ofconstruction and arrangement of parts set forth in the following generaldescription and illustrated in the accompanying drawings, since theinvention is capable of other embodiments and of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology or terminology employed herein is for the purpose ofdescription and not of limitation.

GENERAL DESCRIPTION Shown in FIG. 1 is a snowmobile 11 comprising alongitudinally extending frame 13 including a forward frame portion 17which,in general, provides the bottom wall of an engine compartment orchamber 19. Extending upwardly from the frame 13 and forwardly of thesnowmobile seat 21 (shown fragmentarily) is a I position affordingaccess to the engine compartment 19 and a closed position which, exceptas will be explained, substantiallycloses the engine compartment 19.

In order to reduce sound transmission from the engine compartment 19,and in accordance with the invention, the hood 27 is preferably ofarcuate configuration throughout and is also preferably lined with asound absorbant material, such as a polyurethane foam in blanket form.The interior surface 29 of the transverse partition 23 or dashboard canalso be so lined and, if desired, the interior surface 31 of the frameportion 17 can be so lined. In addition, a soft rubber gasket 33 isdesirably provided at the junction of the hood 27 with the frame portion17 and with the transverse partition 23 so that when the hood 27 isclosed, there is provided a seal between the hood 27 and both of theframe portion '17 and the transverse partition 23, thereby rendering theengine compartment substantially airtight, except as will be explained,and reducing the transmission of noise from the snowmobile generally,and particularly, from the engine compartment.

Also in accordance with the invention, the engine compartment 19 issubdivided by wall means 45 into an air supply chamber 37 and an exitingair chamber 39. Further in accordance with the invention, the air supplychamber 37 is subdivided by additional wall means 41 into an enteringair sub-chamber 43 and a carburetor air supply sub-chamber 47 whichincludes a roof 48, shown fragmentarily in FIG. 1 bridging between thewall means 45 and the additional wall means 81.

Mounted from the frame 13, preferably by conventional resilient mounts(not shown) within the engine compartment 19 and principally in theexiting air chamber 39, is a conventionally constructed internalcombustion engine 49 which can be either of the twostroke or four-stroketype. While various arrangements are possible, in the specificallyillustrated construction, the engine 49 is conventionally constructedand is an oppositely acting two-stroke engine including (see FIG.

2) two air cooled cylinders 50 each including a piston (not shown) andan exhaust port. The engine 49 also includes, as shown in FIG. 1, an aircooling system 61 comprising means (See FIG. 2) defining a cooling airpassage 63 which projects through the wall means and which communicatesbetween the air supply chamber 43 and the exiting air chamber 39. Whilevarious means can be employed, in the specifically illustratedconstruction, such means includes a shroud 65 having an air inlet 67communicating with the entering air subchamber 43 and further havingshroud portions 69 communicating with the exiting air chamber 39 andarranged relative to the cylinders to guide air flow over the enginecylinders 50.

Also included in the engine 49 (See FIG. 2) is a conventional carburetor71 operably communicating with the engine cylinders 50 and including anair inlet 73 communicating, in accordance with the invention, with theair supply chamber 37. In the specifically illustrated construction, thecarburetor air inlet 73 extends through the wall means 41 andcommunicates with the carburetor air supply sub-chamber 47.

In order to supply air to the air supply chamber 37, one or more baffledair inlet means are provided in one or more of the hood 27, transversepartition 23, and frame portion 17. While various arrangements can beemployed, in the illustrated construction, such air inlet meanscommunicates with the entering air subchamber 43 and includes anentering air inlet port 77 provided in the transverse partition 23 onone side of the snowmobile, together with a baffle 79 which ispreferably lined with sound absorbing material and which extends inopposing relation to the entering air port to cause change in thedirection of air flowing into the entering air sub-chamber 37.

The entering air sub-chamber 37 is also arranged to communicate with thecarburetor air supply subchamber 47 through a port 81 in the additionalwall means 41 separating the entering air sub-chamber 43 and thecarburetor air supply sub-chamber 47. Preferably, the port 81 isprovided with a screen, such as a filter, to prevent dirt or debris fromentering into the carburetor air supply sub-chamber 47. Accordingly, except for the entering air inlet port 77, the port 81 between theentering air sub-chamber 43 and the carburetor air supply sub-chamber47, and the engine cooling system air inlet 67, the entering airsub-chamber 43 is substantially closed when the hood 27 is in closedposition.

Except for communication with the port 81 and with the carburetor airinlet 73, the carburetor air supply sub-chamber 47 is substantiallyclosed, independently of the hood or cover 27, and, in order to reducesound emanation from the snowmobile and particularly from the enginecompartment, preferably has a volume exceeding the total displacement ofboth pistons.

The exiting air chamber 39 is also substantially airtight when the hood27 is closed, except for communication through the engine cooling airshroud 67 with the air supply chamber 37 and except for one or morebaffled air outlet means located in one or more of the hood 27,transverse partition 23, and frame portion 17. While variousarrangements can be employed, in the specifically illustratedconstruction, such air outlet means comprises an exiting air port 87located in the transverse partition 23 on the opposite side of thesnowmobile from the entering air port 77. In addition,

the exciting air port 87 is provided with a baffle 89 which ispreferably'lined with sound absorbing material and which is arranged tocause one or more changes in the direction of exiting air flow and todirect exiting air in the direction away from the entering air port 79.

Because of the heat added to the air traveling over the engine cylinders50 during passage of cooling air from the air supply chamber 37 to theexiting air chamber 39, and due to the presence in the exiting airchamber 39 of the mufflers still to be described, the generaltemperature in the exiting air chamber 39 is substantially elevated ascompared to the air'temperature in the air supply chamber 37.

Means are provided in both the entering air sub chamber 43 and thecarburetor air supply sub-chamber 47 for causing changes in direction ofair flow. Preferably, multiple changes in airflow are provided. In thisregard, in the illustrated construction, in the carburetor air supplysub-chamber 47, the wall means defining the carburetor air supply subchamber 47 is so shaped to cause at least one change in air flowdirection during travel from the port 81 to the carburetor air inlet 73.In order to obtain additional air flow directional change, there ispreferably provided a baffle 91 which extends transversely of the flowpath between the port 81 and the carburetor air inlet 73.

In the entering air sub-chamber 43, changes in air flow directions areprovided by baffling the entering air port by the location of the airinlet 67 in the engine shroud 65 in relation to the entering air port77, and by location of a battery 93 or other baffling member in the pathof air travel from the entering air port 77. In the specificallyillustrated construction, the battery 93 is located in opposed orblocking relation to the port 81 connecting the entering air sub-chamber43 and the carburetor air supply sub-chamber 47 to thereby cause airflow direction change.

' Location of the battery 93 in the air flow path in the air supplychamber-37, as compared to the exiting air chamber 39, also serves toretain the battery 93 at a rel- I atively cool operating temperature,particularly as compared to if the battery were located in therelatively hot exiting air'chamber 39. A fuel pump 97 is also desirablylocated in the airsupply chamber 37 so as to prevent excessive heatingof the fuel.

The engine 49 is drivingly coupled to a conventional transmission 99which includes a rotary member 101 arranged so as to be at leastpartially in the path of cooling air flowingfrom the engine shroud 65.The rotary member 101 is driven by the engine 49 by means not a part ofthe invention and includes a series of radially extending andcircumferentially spaced vanes or fins 103 which act as fan bladesduring member rotation, which prevent direct flow of cooling air fromthe engine shroud 65 to the exiting air port 87 and which cause aircirculation within the exiting air chamber 39 of cooling air flowingfrom the engine shroud 65. As a result of the air circulation effectedby the rotating member 101, increased-cooling of the exhaust pipes andmufflers. is achieved, thereby permitting greater noise suppression bythe mufflers.

Also in accordance with the invention, each of the.

two exhaust ports is separately connected by respective exhaust conduitsor pipes 121 and 123 to respective mufflers 127' and 129 which, in turn,are connected to through the frame portion 17, for discharge of exhaustgases underthe snowmobile 11. The separate mufflers 127 and 129 aremounted by suitable straps from the frame portion 17 in parallelrelation to each other in the front portion of the exiting air chamber39. Although one of the features of the invention is the employment of aseparate muffler for each cylinder, nevertheless the mufflers are,except for being left and right handed, of generally identicalconstruction and, accordingly, only the muffler 127 will be described indetail.

The muffler 127 comprises a generally tubular structure which ispreferably double walled including an inner housing 151 and an outerhousing 153 with the area therebetween occupied, at least in part, by asound and temperature insulating material which is substantiallyunaffected by heat. On such fibrous material is CERAFELT which is soldby the K. W. Muth Co. of Sheboygan. i

The inner housing 151 includes a cylindrical wall closed at its end byopposed end walls 155 and 157 which are slightly outwardly dishedtogether with a series of axially spaced first, second, and thirdtransverse baffles or partitions 159, 161 and 163 which divide themuffler 127 into a series of chambers including an end chamber 167located between the end wall 155 and the first partition 159, an outletchamber 169 which is located between the first and second partitions 159and 161 and which communicates with a discharge or exit pipe 171connected to the exhaust pipe 131, a central chamber 173 which islocated between the second and third partitions 161 and 163, and aninlet or megaphone chamber 177 which is defined between end wall 157 andthe third partition 163 and which houses an inlet megaphone 179. Ifdesired, thecentral chamber 173 can be omitted. The axial spacing of thefirst, second and third partitions 159, 161 163 relative to each otherand relative to the end walls 155 and 157 is preferably as generallyshown in the drawings. ln one specific embodiment of the invention, themuffler had an over-all length of approximately 18 inches between theplane of the circumferential periphery of the, end walls and 157 and themegaphone chamber 177 was approximately 10 inches long. The centralchamber 173 was 3 inches long, the outlet chamber 169 was 1 V2 incheslong and the end chamber 167 was 4 A inches long.

The muffler exhaust discharge or exit pipe 171 includes an inlet portion181 communicating with the outlet chamber 169 and extending axially inthe outlet chamber 169 and through the first partition 159. The exhaustpipe further includes an elbow portion 183 which is located in the endchambr 167and which communicates with the inlet portion 181 and with anoutlet portion 187 which extends radially outwardly through ameter ofthe muffler exhaust discharge or exit pipe- 171 is believed to be ofimportance to the proper functioning of the muffler.

The exhaust megaphone 179 includes a flanged inlet potion 191 which isconnected to the exhaust ducts 121 and which extends radially outwardlyfrom the megaphone chamber 177 adjacent to the third partition 163.

The megaphone 179 also includes an elbow portion 193 which is locatedwithin the megaphone chamber 177 and which communicates with the inletportion 191, together with an outlet portion 197 which is also locatedin the megaphonechamber 177, which extends from the elbow portion 193and has an outlet 199 adjacent to the end wall 157, and which has anaxially transverse cross sectional area which increases in the directionfrom the elbow portion 193 toward the outlet 199. In one specificembodiment of the invention, the megaphone 179 had a length along theaxis of the muffler 127 of slightly over 7 /1 inches between the outlet199 and the centerline of the radially extending inlet portion 191. Thelength of the megaphone 179 along the axis of the muffler 127 isbelieved to be of importance to the proper functioning of the muffler.

Located in the end chamber 167 in closely adjacent spaced relation fromthe end wall 155 is a perforated baffle 211 which includes (See FIG. 4)a series of holes or openings 213; In one specific embodiment of theinvention, the baffie 211 was located about A inch from the plane of thecircumferential periphery of the adjacent end wall 155 and the holes 213had a diameter of about A inch. The number of holes 213 and the diameterof the holes 213 provided an open area of about 48 percent of the totalarea of the baffle 211. While the phone chamber 177 into the centralchamber 173 through a pair of generally identical pipes or tubes 221which extend axially'of the muffler 127 and are diametrically spacedfrom each other at a common radius extending between the axis of eachtube to the muffler axis. In one specific embodiment of the invention,the tubes 221 are located at a common radius of about i inches and eachtube 221 has a diameter slightly under 'Va'inch and a length ofapproximately 2 V2 inches. The tube lengths, as well as the employmentof two tubes 221 and the individual tube cross sectional area as well asthe total cross sectional area are believed to be of importance to theproper functioning of the muffler 127. In addition, each tube 221 has aninlet portion 223 projecting into the megaphone chamber 177 for adistance of approximately inch and an outlet portion 227 projecting intothe central chamber 173 for about 2 Vs inches.

I lieved to be important to the proper functioning of the muffler.

In addition to extending completely through the outlet chamber 169, thepipe 231 has an inlet portion 233 projecting into the central chamber173 and an outlet portion 237 projecting into the end chamber 167. Theamount of projection into the central chamber 173 and end chamber 167can be varied as desired, except that it is believed to be important tothe proper functioning of the muffler that the projecting outletportions 227 of the pipes 221 axially overlap the projecting inletportion 233 of the pipe 231 so as to require circuitous travel withinthe central chamber 173 from the pipes 221 to the pipe 231. The amountof overlap may be varied as desired.

In the end chamber 167, gas flows through the holes 213 in the baffle211 and then reverses direction after striking the end wall and thentravels back through the holes 213 in the baffle 211.

From the end chamber 167, exhaust gas flows to the outlet chamber 169through a pair of generally identical pipes 241 which are diametricallyspaced from each other at a right angle with respect to the diametricspacing of the pipes 221 and at a common radius extending between theaxis of each tube 241 to the muffler axis. In one specific embodiment ofthe invention, the pipes or tubes 241 each have an inner diameter ofslightly less than /8 inch and a length of approximately 1 inch. Thetube lengths, the employment of two tubes, and the individual tube crosssectional areas, as well as total cross sectional area, are believed tobe of importance to the proper functioning of the muffler. Each of thepipes includes an inlet portion 243 which projects into the end chamber167 and an outlet portion 247 which projects into the outlet chamber169. However, the length of such projecting portions can be varied asdesired.

Various of the features of the invention are set forth in the followingclaims.

I claim:

1. A muffler comprising a generally tubular housing having opposed endwalls, a first barrier spaced axially from one of said end walls anddefining, with said one end wall, an end chamber, a second barrierspaced axially from said first barrier in the direction away from saidone end wall and defining, with said first barrier, an outlet chamber, athird barrier spaced axially from said second barrier in the directionaway from said one end wall and defining, with said second barrier, acentral chamber and defining, with the other of said opposed end walls,a megaphone chamber, a single exhaust megaphone in said megaphonechamber and including an outlet portion terminating adjacent to saidother end wall, a first pipe extending from said megaphone chamber tosaid central chamber, a second pipe extending from said central chamberto said end chamber, a third pipe extending from said end chamber tosaid exhaust chamber, and an exhaust discharge pipe having a dischargeportion extending from said outlet chamber outwardly of said housing.

2. A muffler comprising a generally tubular housing having opposed endwalls, a perforated baffle in adjacently spaced and parallel relation ofone of said opposed end walls, a first barrier spaced axially from saidperforated baffle in the direction away from said one end wall anddefining, with said one end wall, an end chamber, a second barrierspaced axially from said first barrier in the direction away from saidone end wall and defining, with said first barrier, an outlet chamberand defining, with the other of said opposed end walls, a megaphonechamber, a single exhaust megaphone in said megaphone chamber andincluding an outlet portion terminating adjacent to said other end wall,passage means connecting said megaphone chamber to said end chamber, apipe extending from said end chamber to said exhaust chamber, and anexhaust dis- 9 charge pipe including a discharge portionextending fromsaid outlet chamber outwardly of said housing.

3. A muffler comprising a generally tubular housing having opposed endwalls, a perforated baffle in adjacently spaced and parallel relation toone of said opposed, end walls, a first barrier spaced axially from saidperforated baffle in the direction away from said one end wall anddefining, with said one end wall, an end chamber, a second barrierspaced axially from said first barrier in the direction away from saidone end wall and defining, with said first barrier, an outlet chamber, athird barrier spaced axially from said second barrier in the directionaway from said one end wall and defining, with said second barrier, acentral chamber and defining, with the other of said opposed end walls,a

megaphone chamber, a single exhaust megaphone in said megaphone chamberand including an inlet portion extending radially outwardly from saidmegaphone chamber and having an outlet portion extending at a rightangle to said inlet portion and terminating adjacent to said other endwall, a first tubular pipe extending from said megaphone chamber to saidcentral chamber, a second tubular pipe extending from said centralchamber to said end chamber, a third tubular pipe extending from saidend chamber to said outlet chamber, and an exhaust discharge pipe havingan inlet portion extending in. said outlet chamber, and a dischargeportion extending from said inlet portion and outwardly of said housing.

1. A muffler comprising a generally tubular housing having opposed endwalls, a first barrier spaced axially from one of said end walls anddefining, with said one end wall, an end chamber, a second barrierspaced axially from said first barrier in the direction away from saidone end wall and defining, with said first barrier, an outlet chamber, athird barrier spaced axially from said second barrier in the directionaway from said one end wall and defining, with said second barrier, acentral chamber and defining, with the other of said opposed end walls,a megaphone chamber, a single exhaust mEgaphone in said megaphonechamber and including an outlet portion terminating adjacent to saidother end wall, a first pipe extending from said megaphone chamber tosaid central chamber, a second pipe extending from said central chamberto said end chamber, a third pipe extending from said end chamber tosaid exhaust chamber, and an exhaust discharge pipe having a dischargeportion extending from said outlet chamber outwardly of said housing. 2.A muffler comprising a generally tubular housing having opposed endwalls, a perforated baffle in adjacently spaced and parallel relation ofone of said opposed end walls, a first barrier spaced axially from saidperforated baffle in the direction away from said one end wall anddefining, with said one end wall, an end chamber, a second barrierspaced axially from said first barrier in the direction away from saidone end wall and defining, with said first barrier, an outlet chamberand defining, with the other of said opposed end walls, a megaphonechamber, a single exhaust megaphone in said megaphone chamber andincluding an outlet portion terminating adjacent to said other end wall,passage means connecting said megaphone chamber to said end chamber, apipe extending from said end chamber to said exhaust chamber, and anexhaust discharge pipe including a discharge portion extending from saidoutlet chamber outwardly of said housing.
 3. A muffler comprising agenerally tubular housing having opposed end walls, a perforated bafflein adjacently spaced and parallel relation to one of said opposed endwalls, a first barrier spaced axially from said perforated baffle in thedirection away from said one end wall and defining, with said one endwall, an end chamber, a second barrier spaced axially from said firstbarrier in the direction away from said one end wall and defining, withsaid first barrier, an outlet chamber, a third barrier spaced axiallyfrom said second barrier in the direction away from said one end walland defining, with said second barrier, a central chamber and defining,with the other of said opposed end walls, a megaphone chamber, a singleexhaust megaphone in said megaphone chamber and including an inletportion extending radially outwardly from said megaphone chamber andhaving an outlet portion extending at a right angle to said inletportion and terminating adjacent to said other end wall, a first tubularpipe extending from said megaphone chamber to said central chamber, asecond tubular pipe extending from said central chamber to said endchamber, a third tubular pipe extending from said end chamber to saidoutlet chamber, and an exhaust discharge pipe having an inlet portionextending in said outlet chamber, and a discharge portion extending fromsaid inlet portion and outwardly of said housing.